do all fieros come with the red connector for the bass speaker under the glove box area?

I would think probably not, since that wire goes to the sub-woofer amp that is only on performance sound equipped cars.

what does one need to install this system into the car?

Amp, wiring harness, sub and enclosure. The overhead slider is optional, I chose not to install it because I didn't want to take my A-Pillar off and possibly break it.

which wiring harness?

It's a wiring harness that connects between the head unit and the car's radio plug, and it also has a connector for the amp, (possibly a connector for the overhead slider), and lastly a connector for the sub. The amp is located behind the carpet on the passenger side in the center console, down by the floor. You can post a for sale thread in the mall asking for a harness, there's many people with extras. I got mine for $25.

You'll need all the factory parts.
http://calgaryfieros.com/OSGdocs/subwoofer.html

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Its not that hard to install them. Mostly plug and play. Make sure you get the cover for your heater core that has the sub mounting bracket on it.

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quote Originally posted by Fiero Thomas: Its not that hard to install them. Mostly plug and play. Make sure you get the cover for your heater core that has the sub mounting bracket on it.

This is not in anyway a hard install,and it actually makes a good difference in a stock/mild aftermarket head unit....Enjoy...

trying to remove the system to sell it, Anyone got a photo of the harness.

I am removing everything, I dunno what to remove, I am trying to remove the entire dash harness.

[This message has been edited by zipper9 (edited 11-22-2014).]

quote Originally posted by zipper9: trying to remove the system to sell it, Anyone got a photo of the harness. I am removing everything, I dunno what to remove, I am trying to remove the entire dash harness.

The previous picture shows the radio, amplifier and subwoofer harness.
Here's the one showing the subwoofer wiring routing to the overhead light switch.